Study: Preterm Babies Have Different Gut Microbes ― Which Could Affect Their Health

A team of researchers at Washington University has found that babies born prematurely have very different gut microbes than those of babies carried to term.

Dr. Barbara Warner (left) and nurse Laura Linneman check on infant Skylar Angel in the neonatal intensive care unit at St. Louis Children's Hospital. Skylar and her twin, Bayley, were born prematurely.

Credit Elizabethe Holland Durando, Washington University School of Medicine

All children are born with almost no microbes in their intestines. Their gut microbial communities develop quickly in the weeks after birth ― although the communities don't reach full maturity until children are 2 or 3 years old.

But little is known about how this microbial development occurs.

This study, which was co-authored by Washington University neonatologist Dr. Barbara Warner, focused on premature infants.

She and her colleagues collected stool samples from 58 infants in the neonatal intensive care unit at St. Louis Children's Hospital ― about 60,000 samples in all.

Using DNA sequencing, the researchers identified the bacteria and other microbes in 922 of the samples.

Warner said they found much less diversity in the types of microbes in the guts of these premature infants than is typical in infants born at term ― something they expected based on previous research.

Their next finding came as more of a surprise: “Regardless of the age of the infant at birth, regardless of the type of diet, regardless of the antibiotic exposures, the microbial population progressed in a fairly standard manner to a population that became very similar around reaching term age," Warner said.

The researchers found that three major classes of bacteria — Bacilli, Gammaproteobacteria and Clostridia — colonized the guts of premature infants in a predictable sequence after birth.

Credit Phillip I. Tarr, Washington University School of Medicine

In other words, the gut microbial composition of preterm infants was much more consistent than that of babies carried to term. For full-term babies, the gut microbial communities can differ widely based on environmental factors, like whether they were delivered by vaginal birth or Caesarean section, or whether they’re fed breast milk or formula.

“So there is something unique about that pre-term population that results in a different colonization pattern than term infants,” Warner said.

That matters, she said, because there’s more and more evidence that the microbes in our guts can have long-term health effects that go beyond our digestive system.

All of this raises the question: How does being born preterm, and having a very different microbial population, impact a child’s health and development. “Whether it’s the central nervous system, the brain, or whether it’s our long-term immune response, those are the kinds of questions that we’re just starting to ask,” Warner said.

Gut microbes and long-term health

Premature infants are susceptible to life-long problems and Warner believes it’s possible that their immature gut bacteria are playing a role in that.

The current research, which is published in the Proceedings of the National Academy of Sciences, is the first in a series of studies funded by the National Institutes of Health, focusing on a specific life-threatening disease that affects preterm infants.

The condition affects approximately 10 percent of preterm infants, killing part or all of their intestinal lining. It's fatal in about 30 percent of cases.

"Our next step is to compare these, what we would call normal preterm infants, with infants who go on to develop this severe inflammatory process," Warner said.

If they find differences between the two groups in the colonization patterns of their microbial communities, then that could help to explain why some babies develop this life-threatening problem, and others do not.

“And that’s important,” Warner said. “Because if we can understand the reasons behind what causes this inflammation, we then are at a point where we can much better intervene and prevent ― not just treat, but prevent ― that from occurring.”